This invention relates generally to the field of golf clubs, and more particularly to the field of golf club shafts having variations in flexibility along certain portions of the shaft, and even more particularly relates to golf club shafts wherein the variation in flexibility occurs in the grip portion.
Steel and graphite composite golf club shafts both have a graduated bend when flexed. Shafts can be designed to be stiffer or more flexible depending on the particular club, the ability of the golfer, etc. The amount of bend in a standard golf shaft is gradually progressive, in that the flex is greater near the tip end, i.e., the club head end, than near the butt or grip end. The flex of the golf shaft enables the golfer to generate increased club head speed, as the shaft bends and then recoils when striking the golf shot. Professional golfers use a stiffer, less flexible shaft because they can then attain the optimum distance with more control. Most golfers, however, need a more flexible shaft in order to maximize club head speed as the ball is struck—the key factor in driving distance. There is a trade-off, however, between power and control, because the more flexible shafts, while increasing distance, have more twist or torque. Torque resistance is desirable in a golf shaft because most golfers do not hit the ball in the center of the clubface. When the ball is hit off-center toward the heel or toe of the club head, the shaft twists and the ball is propelled to the left or right in an exaggerated and undesirable manner. Consequently, there is a need to balance increased distance with loss of control.
The USGA in its “Rules of Golf” requires that at any point along the length of the shaft, the shaft shall bend in such a way that the deflection is the same regardless of how the shaft is rotated about the longitudinal axis and shall twist the same amount in both directions. In other words, there cannot be any preferential deflection in the shaft in a chosen direction, such as in the direction parallel to the perfect shot direction.
Standard golf shafts are tubular members of diminishing diameter progressing from the butt or grip end (the proximal end held by the golfer) to the tip end (the end connected to the club head). The flex of the shaft is determined primarily by the diameter of the shaft. If the diameter is wider throughout the shaft, it will be stiffer than a shaft constructed of similar material that is thinner in diameter through the shaft. The flex and torque of the shaft can be controlled more in graphite shafts as opposed to metal shafts thorough selectivity and application of resins and carbon fiber materials. However, in the traditional design, it is difficult for either steel or graphite shaft makers to significantly alter the flex point of the shaft or create other desirable performance characteristics in a shaft.
Attempts to optimize golf club shaft design and structure can be seen in U.S. Pat. No. 5,842,930 to Koterba, U.S. Pat. No. 5,733,204 to Carrara, U.S. Pat. No. 2,250,429 to Vickery, U.S. Pat. No. 5,735,752 to Antonious, U.S. Pat. No. 6,024,651 to Cheng, U.S. Pat. No. 6,042,485 to Cheng, U.S. Pat. No. 6,280,347 to Herber, U.S. Pat. No. 5,439,219 to Vincent, U.S. Patent Application Publication No. 2001/0012803 to Feeney, and U.S. Patent Application Publication No. 2002/0098907 to Hsu. These devices have failed to provide an optimum solution to the problem of balancing control and distance.
It is an object of this invention to provide a golf club wherein the flex is optimized relative to standard golf club shaft construction. It is a further object to provide a golf shaft and club of improved flex and control wherein the improved flexibility occurs at or near the proximal end of the golf club, i.e., within the upper butt section or grip portion of the club.